forsyth:

add c11 _Noreturn decoration.  

Reference: /n/atom/patch/applied/ccnoreturn
Date: Sun Aug 16 01:17:01 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/cc/cc.h	Sun Aug 16 01:16:04 2015
+++ /sys/src/cmd/cc/cc.h	Sun Aug 16 01:16:06 2015
@@ -363,7 +363,8 @@
 	GXXX		= 0,
 	GCONSTNT	= 1<<0,
 	GVOLATILE	= 1<<1,
-	NGTYPES		= 1<<2,
+	GNORETURN	= 1<<2,
+	NGTYPES		= 1<<3,
 
 	GINCOMPLETE	= 1<<2,
 };
--- /sys/src/cmd/cc/cc.y	Sun Aug 16 01:16:08 2015
+++ /sys/src/cmd/cc/cc.y	Sun Aug 16 01:16:10 2015
@@ -64,7 +64,7 @@
 %token	LIF LINT LLONG LREGISTER LRETURN LSHORT LSIZEOF LUSED
 %token	LSTATIC LSTRUCT LSWITCH LTYPEDEF LTYPESTR LUNION LUNSIGNED
 %token	LWHILE LVOID LENUM LSIGNED LCONSTNT LVOLATILE LSET LSIGNOF
-%token	LRESTRICT LINLINE
+%token	LRESTRICT LINLINE LNORETURN
 %%
 prog:
 |	prog xdecl
@@ -1149,6 +1149,7 @@
 	LCONSTNT { $$ = BCONSTNT; }
 |	LVOLATILE { $$ = BVOLATILE; }
 |	LRESTRICT { $$ = 0; }
+|	LNORETURN { $$ = 0; }
 
 name:
 	LNAME
--- /sys/src/cmd/cc/lex.c	Sun Aug 16 01:16:13 2015
+++ /sys/src/cmd/cc/lex.c	Sun Aug 16 01:16:14 2015
@@ -1135,6 +1135,7 @@
 	ushort	type;
 } itab[] =
 {
+	"_Noreturn",	LNORETURN,	0,
 	"auto",		LAUTO,		0,
 	"break",	LBREAK,		0,
 	"case",		LCASE,		0,